Ad-hoc Network

Description

An Ad-hoc Network is a dynamically organized network of mobile terminals that are able to communicate with each other via some means, such as IEEE 802.15 or WLAN in ad-hoc mode. In the context of 3GPP, the term is primarily used in the study of Ambient Networks and the Ambient IP Network (AIPN), as documented in TR 22.978 and TS 22.258. The Ad-hoc Network may contain terminals that are capable of connection to a variety of access systems, and it is assumed that every terminal in the Ad-hoc Network is under the control of a separate user, each able to independently access the AIPN. The Ad-hoc Network routes their consolidated traffic towards the AIPN, to an access system through one or more terminals in the Ad-hoc Network. The terminal carrying the consolidated traffic may change dynamically according to rules set up by the users, and the Ad-hoc Network may move throughout the geographic coverage area.

The concept of an Ad-hoc Network in 3GPP is closely tied to the vision of ubiquitous connectivity and cooperative networking. Unlike traditional cellular networks where terminals communicate directly with base stations, an Ad-hoc Network allows terminals to relay traffic for each other, extending coverage and improving capacity. This is particularly useful in scenarios where direct coverage is unavailable or unreliable, such as in disaster relief, military operations, or remote areas. The Ad-hoc Network can also be used to aggregate traffic from multiple users, reducing the number of simultaneous connections to the access network and improving spectral efficiency.

The architecture of an Ad-hoc Network in the AIPN context involves several key components. First, the terminals must be capable of forming an ad-hoc network, which requires a common radio interface and a protocol for neighbor discovery and routing. Second, the network must have a mechanism for selecting the gateway terminal that will route the consolidated traffic to the access network. This selection can be based on various criteria, such as signal strength, battery life, or user preferences. Third, the network must support dynamic reconfiguration, as terminals may join or leave the network, and the gateway may change. Finally, the network must ensure security and privacy, as the traffic is relayed through multiple terminals.

The Ad-hoc Network concept has been studied in 3GPP primarily in the context of AIPN, which was a study item in Rel-7 and Rel-8. The goal was to define an architecture that allows mobile terminals to form an ambient network that can dynamically adapt to changes in the environment and user requirements. The Ad-hoc Network is a key enabler of this vision, as it allows terminals to cooperate and share resources. However, the concept has not been widely adopted in commercial cellular networks, partly due to the complexity of managing ad-hoc networks and the lack of a clear business model. Nevertheless, the idea of cooperative networking has seen renewed interest in the context of 5G and beyond, with technologies such as device-to-device (D2D) communication, integrated access and backhaul (IAB), and relay nodes.

In summary, the Ad-hoc Network is a dynamically organized network of mobile terminals that communicate directly with each other and can route traffic to an access network. It is a key concept in the AIPN study and represents an early vision of cooperative networking in 3GPP. While not widely deployed, it has influenced the development of later technologies such as D2D and IAB.

Purpose & Motivation

The Ad-hoc Network concept exists to enable mobile terminals to communicate and cooperate without relying solely on fixed infrastructure. In traditional cellular networks, terminals must be within coverage of a base station to communicate. This limits connectivity in areas with poor coverage or during emergencies when infrastructure may be damaged. An Ad-hoc Network allows terminals to relay traffic for each other, extending coverage and enabling communication even when direct access to the network is unavailable.

The motivation for the Ad-hoc Network in 3GPP came from the Ambient Networks project, which envisioned a future where networks are dynamically created and dissolved based on user needs. The AIPN study in Rel-7 and Rel-8 aimed to define an architecture where terminals can form an ambient network and cooperatively route traffic to an access system. The Ad-hoc Network was a key component of this vision, providing the means for terminals to communicate directly and share resources.

However, the Ad-hoc Network concept faced several challenges. Managing a dynamic network of mobile terminals is complex, requiring sophisticated routing and security protocols. The lack of a clear business model and the prevalence of affordable cellular coverage also limited its adoption. Despite these challenges, the concept has influenced later developments such as D2D communication in LTE and NR, which allow direct communication between devices, and IAB, which uses relay nodes to extend coverage. The Ad-hoc Network thus represents an important step in the evolution of cooperative networking in 3GPP.